This invention relates generally to throttle control of diesel electric locomotives and in particular to control of the number of locomotives providing tractive effort for a freight train where maximum tractive effort is only required for a portion of the freight movement. It is well known that for the majority of diesel electric locomotives in operation today, manufacturers have, in order to provide desired tractive characteristics, designed units where high efficiency occurs at one or perhaps two throttle settings. Therefore, operation of a locomotive at other than a pre-selected throttle setting results in measurable reduction in ton miles per gallon of fuel consumed.
Present freight handling requirements have resulted in trains of a hundred or more cars operating on roadbeds where the horsepower requirements vary from one horsepower/ton to six horsepower/tons. This variation is due to existing weather conditions, grades and speeds to meet trains schedules. It is highly desirable to operate the present modern diesel electric locomotives at a throttle setting very near its maximum rated horsepower, however, when several locomotives are needed to pull a substantial train over a distance where variation in tractive effort is encountered, present control methods wherein each power unit, controlled from a single lead unit operates at identical throttle settings, resulting in relatively poor fuel economy.
Recent dramatic increases in fuel costs were not foreseen during the initial design of currently operating locomotives, therefore it is necessary to provide control equipment which allows operation of a multiple locomotive train over a extremely wide range of horsepower or individual unit throttle settings. Existing "trainline" control utilizes a highly reliable system of control wires passing through each locomotive and actuating the governors of the individual locomotives. In this way although the governor adjusts the specific fuel consumption for loads imposed on the unit, the maximum horsepower available is limited by the particular throttle position of the locomotive electrohydraulic governor. The most commonly used governors provide eight throttle settings allowing operators to utilize the inherent advantages of the diesel electric locomotive to provide increased torque for train starting and higher speed when under way. However as indicated above, the maximum efficiency occurs in at most two of the eight settings, therefore utilizing the present control system, maximum fuel economy only occurs at or near the maximum total horsepower requirement, since all units follow the lead throttle setting. With this system when operating under moderate horsepower requirements it is necessary to operate each unit at a relatively inefficient low throttle setting resulting in reduced fuel economy.
In a known unit which provides individual control of locomotives in multiple locomotives trains or consists, a relatively complicated switching system is utilized which employs two trainline wires. Additionally, individual units must be selected, i.e., each lead and training locomotive must be specifically adjusted for its position in the consists in order to be properly controlled. Control switches are used on each unit to pre-select each unit as to its position in the consist. This requires an extra employee assignment or added duties for existing personnel to perform. This requirement has substantial shortcomings when it is necessary to "break up locomotive consists" or separate units from other units in a consist add or remove units.
At major rail terminating terminals the train consists or makeup of locomotives and cars are broken up, separated or turned, to make up a new train for a return trip. Engines are controlled by action of a manual selector switch, requiring individual adjustments of each locomotive. Another disadvantage of the known unit is that engines are controlled by energizing one or two trainline wires or both trainline wires used. This usually limits the reduction of units to 3 locomotive units. When switching from one unit in reduced power mode to two units in reduce mode, three units are reduced monentarily. This can cause an excessive reduction of power at times.
Therefore, the invention disclosed here provides a method which is insensitive to position in the train, and therefore does not require individual settings, utilizes only one trainline wire, is self-compensating in the case of inadvertent connection of a lead unit in a trailing position and provides a relatively uncomplicated indication of the operating units, wherein each is adjusted to its maximum efficiency. The system and devices disclosed will control more locomotive units, with finer control of the locomotives.